What does the cryptic crossword clue "Tool reportedly used to underpin ginormous bone (7)" mean?

The definition is "bone". The wordplay uses a homophone (sounds like). OS – huge & what sounds like SICKLE The answer is OSSICLE.

Tool reportedly used to underpin ginormous bone (7)

Independent Cryptic #11878 | 21 Down | 2024-11-04 flower